Question

Distant galaxies are seen by astronomers to be red-shifted.
What wave principle explains this, and what does this observation mean about the universe?

• A. Diffraction; the universe is very old
• B. Refraction; the universe is expanding
• C. Polarization; the universe in infinite
• D. Doppler effect; the universe is expanding
• E. Diffraction; the universe is expanding

Answer 1

The correct option is D Doppler effect; the universe is expanding

This statement is explained by Doppler Effect.

Astronomers have found that the further from us a star is, the more its light is red-shifted. This tells us that distant galaxies are moving away from us, and that the further away a galaxy is, the faster it's moving away.